The present invention relates to a unit for overwrapping products, packets in particular, and to a relative overwrapping method.
The invention finds application to advantage in the tobacco industry, where sheets of transparent material obtained from a continuous strip are used to overwrap packets of tobacco products, typically packets of cigarettes, to which reference is made explicitly in the following specification albeit implying no limitation in general scope.
More particularly, the present invention relates to a unit for overwrapping packets substantially of rectangular prismatic shape delimited axially by two end faces, and laterally by two larger faces and two smaller faces extending parallel to the longitudinal axis of the rectangular prism.
An overwrapping unit of the type in question comprises a feed device dispensing single wrapping sheets cut from a decoiling roll of continuous strip material, and the operation of overwrapping the packets is accomplished as the packets advance along a predetermined wrapping path, utilizing a plurality of folder mechanisms by which each packet is enveloped completely in a respective sheet.
Given the high output speeds of modern cigarette makers and packers, to which overwrapping units of the above noted type are linked, there is a growing need, if the overwrapped products are to emerge free of imperfections, for the single sheets of overwrapping material to be kept continuously and fully under control along the entire wrapping path and throughout the successive operations performed by the folder mechanisms, so as to avoid any possibility of a misalignment between the packet and the sheet, or a portion of the sheet, that could result in the finished overwrap presenting unsightly creases or blemishes.
Importantly, this need for complete control over the sheets is especially evident along stretches of the wrapping line that extend between areas where successive folder mechanisms operate, and more precisely along the stretches where, with the overwrap still not fully formed, one or more parts of the sheet still project freely and have yet to undergo the action of a fold-making element.
The object of the present invention is to provide a unit for overwrapping packets such as will meet the requirements indicated above, while operating at the high output speeds of which modern cigarette makers and packers are capable.